個人計算機領域流行用智能電池，這是因為智能電池能提供本個工業標準、高精度氣壓計（gasgauge）系統。智能電池符合智能電池供電系統（SBS）所定義的元件所有工作性能指標，電池具有跟蹤有關電池充電和使用信息的嵌入控制器。通過串行、2線SMBus接口提供信息到系統。可詢問電池信息包括剩余容量、總容量、在現有放電速率下時間余、放電電流、終端電壓等。由于大多數智能電池在總線中可成為主機，所以電池可控制智能電池充電器使其最佳充電。Linear公司LTC1759智能電池充電器IC設計用于控制這類智能電池。另(ling)外(wai)，由電池提供的安全(quan)信(xin)號指示電池是否(fou)呈(cheng)現(xian)在系統中和是否(fou)有熱(re)引(yin)起的告警或在其他系統失效時是否(fou)電池失效。SBS顯著(zhu)特(te)點是安全(quan)、使用容(rong)易和兼容(rong)性。

　　SBS規范允許兩種類型智能電池充電器（SBC）：Level2充電和Level3充電器。Level2充電器（如LTC1759）是SMBus上的從機，響應來自電池的命令控制充電。Level3充電器可以是SMBus上的主機或從機，它可詢問電池確定充電信息。SBC與電池化學類型無關。它響應來自電池的命令提供充電電流和充電電壓。電池的零電流（或零電壓）或終止充電報警形式發出充電終止。假若安全信號指標電池不存在或安全充電電池太熱，則充電也將(jiang)終止。

　　SMBus 為(wei)系(xi)(xi)統(tong)(tong)和(he)電(dian)(dian)源(yuan)管理(li)這樣(yang)的(de)(de)(de)(de)(de)任(ren)務提供(gong)了(le)一條(tiao)控(kong)制總(zong)線(xian)，使(shi)用(yong)(yong)(yong) SMBus 的(de)(de)(de)(de)(de)系(xi)(xi)統(tong)(tong)，設(she)備(bei)之(zhi)間(jian)發送(song)和(he)接收(shou)消息都是通(tong)(tong)過 SMBus，而不是使(shi)用(yong)(yong)(yong)單獨的(de)(de)(de)(de)(de)控(kong)制線(xian)，這樣(yang)可(ke)(ke)以(yi)節省設(she)備(bei)的(de)(de)(de)(de)(de)管腳數。 　　使(shi)用(yong)(yong)(yong) SMBus，設(she)備(bei)還(huan)可(ke)(ke)以(yi)提供(gong)它(ta)的(de)(de)(de)(de)(de)生產(chan)信息，告訴系(xi)(xi)統(tong)(tong)它(ta)的(de)(de)(de)(de)(de)型(xing)號，部件(jian)號等(deng)(deng)，針對掛(gua)起(qi)事件(jian)保(bao)存它(ta)的(de)(de)(de)(de)(de)狀(zhuang)態，報告不同(tong)類別的(de)(de)(de)(de)(de)錯誤(wu)，接收(shou)控(kong)制參數，并返回它(ta)的(de)(de)(de)(de)(de)狀(zhuang)態等(deng)(deng)。 　　SMBus器(qi)件(jian)存在(zai)現(xian)有(you)7層(ceng)(ceng)(ceng)OSI網(wang)(wang)絡模(mo)型(xing)中的(de)(de)(de)(de)(de)前(qian)3層(ceng)(ceng)(ceng)，即物理(li)層(ceng)(ceng)(ceng)，數據鏈(lian)路(lu)層(ceng)(ceng)(ceng)和(he)網(wang)(wang)絡層(ceng)(ceng)(ceng)。 　　SMBus最初(chu)的(de)(de)(de)(de)(de)目的(de)(de)(de)(de)(de)是為(wei)智(zhi)能電(dian)(dian)池(chi)，充電(dian)(dian)電(dian)(dian)池(chi)和(he)與其他系(xi)(xi)統(tong)(tong)通(tong)(tong)信的(de)(de)(de)(de)(de)微(wei)控(kong)制器(qi)之(zhi)間(jian)的(de)(de)(de)(de)(de)通(tong)(tong)信鏈(lian)路(lu)而定義的(de)(de)(de)(de)(de)。SMBus也被用(yong)(yong)(yong)來連接各種設(she)備(bei)，包括(kuo)電(dian)(dian)源(yuan)相(xiang)關設(she)備(bei)，系(xi)(xi)統(tong)(tong)傳感器(qi)，EEPROM通(tong)(tong)訊設(she)備(bei)等(deng)(deng)等(deng)(deng)。

　　LTC1759是一款完整的Level2智能電池充電器。它能在SMBus接口上用接收和譯碼命令自動充電智能電池。LT1759遵從智能電池充電器規范的(de)全(quan)部安全(quan)要(yao)求，包括3分鐘定時器（保(bao)護(hu)SMBus通信換效和喚醒模式(shi)期間鋰離子(zi)電(dian)池過(guo)充電(dian)）。硬件(jian)可(ke)編(bian)程電(dian)注和電(dian)壓(ya)限制提供(gong)另(ling)外等級(ji)保(bao)護(hu)，這種保(bao)護(hu)由失效軟件(jian)不可(ke)能改變。

　　LTC1759管理智能電池充電系統的所有復雜事物。它具有SBC依從性、安全、輸出電壓精確、SMBus加速泵、墻式適配器電流限制等特性。它把智能充電器的恒流（CC）、恒壓（CV）、電流模式開關電池充電器電路融合于一身。

　　電路描述

　　LTC1759包括：一個同步、電流模式、PWM降壓開關控制器，一個充電器控(kong)制(zhi)(zhi)器(qi)(qi)，兩個(ge)控(kong)制(zhi)(zhi)充電器(qi)(qi)參量的10位DAC，一個(ge)熱敏(min)電阻安全信號譯碼器(qi)(qi)，硬件電壓(ya)和電流限制(zhi)(zhi)譯碼器(qi)(qi)和一個(ge)SMBus控(kong)制(zhi)(zhi)器(qi)(qi)單元（見圖1）。

 智能(neng)電(dian)池或系(xi)統控制(zhi)器通過SMBus接(jie)口(kou)命令對恒(heng)漢和(he)恒(heng)壓(ya)限(xian)值(zhi)進行(xing)編程。降壓(ya)變壓(ya)器用(yong)N-溝MOSFET做為開關，使成本降低(di)、高效率(lv)工作。熱敏電(dian)阻安(an)全檢測電(dian)路檢測電(dian)池存在或確(que)定(ding)電(dian)池溫度是否允(yun)許安(an)全充電(dian)。

當(dang)(dang)通過(guo)SMBus傳輸接收(shou)恒(heng)流(liu)(liu)(liu)(liu)(liu)值時，它被RILIMIT定標(biao)和限(xian)制到低(di)于編(bian)程(cheng)值。此(ci)修正值編(bian)程(cheng)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)DAC，設置(zhi)DC充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)。電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)DAC是10位△∑DAC，當(dang)(dang)希望(wang)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)時，它從PROG引(yin)腳(jiao)吸收(shou)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)（見圖(tu)2）。放大器(qi)PROG引(yin)腳(jiao)吸收(shou)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)（見圖(tu)2）。放大器(qi)CAI感測RSENSE上(shang)的(de)(de)壓降(jiang)并使此(ci)電(dian)(dian)(dian)(dian)壓跨(kua)接到RS2（200Ω）；流(liu)(liu)(liu)(liu)(liu)經(jing)RS2的(de)(de)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)通過(guo)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)鏡像做為PROG引(yin)腳(jiao)上(shang)的(de)(de)上(shang)接電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)。流(liu)(liu)(liu)(liu)(liu)經(jing)RS2電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)與來自PROG引(yin)腳(jiao)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)相匹配由(you)CA2實現(xian)恒(heng)流(liu)(liu)(liu)(liu)(liu)工作(zuo)。由(you)于DAC輸出是一串脈(mo)沖，所(suo)以(yi)需要平滑(hua)電(dian)(dian)(dian)(dian)容器(qi)對脈(mo)沖濾波(bo)使其(qi)變(bian)為DC。

  LTC1759需要兩(liang)個(ge)電源。PWM電路在墻式適配器電源斷開時直(zhi)接通(tong)過Vcc引腳運(yun)行，邏(luo)輯(ji)功(gong)能(neng)運(yun)行與VDD電源無關。PWM電路在去掉AC電源時能(neng)進入40μA微(wei)功(gong)率停(ting)機(ji)模式，使邏(luo)輯(ji)和SMBus工作(zuo)能(neng)保持運(yun)行，這(zhe)是(shi)Intel ACPI標準所需要的。這(zhe)種(zhong)分離電源也使邏(luo)輯(ji)和SMBus能(neng)根據(ju)系統設計為員的需要運(yun)行在3V和5V.為使LTC1759邏(luo)輯(ji)功(gong)耗最小，邏(luo)輯(ji)電流由時鐘電路激勵，時鐘電路當無動作(zuo)時停(ting)機(ji)并(bing)蘇醒服務(wu)于SMBus動作(zuo)或產生中斷。一旦請(qing)求服務(wu)，LTC1759便返回到休眠(mian)。

　　當去掉AC電(dian)源或去掉電(dian)池時，通過(guo)(guo)CHGEN-SDB引腳(jiao)(jiao)組合發生PWM停機(ji)(ji)。LTC1759通過(guo)(guo)DCDIV通腳(jiao)(jiao)檢測AC損耗。閾值通常設置恰好低(di)于墻式適配的最小有(you)效電(dian)壓。AC電(dian)源狀態(tai)通過(guo)(guo)SMBus可由(you)系統(tong)讀出。UV引腳(jiao)(jiao)只用于置PWM電(dian)路進(jin)入(ru)微功率停機(ji)(ji)狀態(tai)，它直(zhi)接連到墻式適配器電(dian)源。

　　在設計(ji)中電(dian)感器(qi)選(xuan)擇(ze)不(bu)是關鍵(jian)，這是因(yin)為充電(dian)器(qi)的(de)環路響應在意地(di)設置很慢。實際的(de)低限值為15μH左右，低值電(dian)感器(qi)將產生較高的(de)紋波電(dian)流，在輸出(chu)需要(yao)較低ESR電(dian)容器(qi)。

　　輸(shu)(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)的選擇(ze)(ze)對ESR（等效串聯(lian)(lian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻）不是(shi)很(hen)苛刻，但必須(xu)處理(li)來(lai)自充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)(qi)(qi)的所有(you)(you)(you)紋(wen)波電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流。不用(yong)考(kao)慮(lv)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的紋(wen)波電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流，因(yin)為(wei)(wei)(wei)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)(qi)(qi)有(you)(you)(you)效阻抗(kang)遠遠大于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感器(qi)(qi)(qi)(qi)(qi)的ESR。很(hen)多電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)組具有(you)(you)(you)內部串聯(lian)(lian)保護MOSFET，這提高了電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)ESR。在多電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)配置中也(ye)有(you)(you)(you)與電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)串聯(lian)(lian)的功率路由MOSFET，進一步增(zeng)加(jia)了電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)ESR。從充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)(qi)(qi)觀點，輸(shu)(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)(qi)(qi)ESR可(ke)高達1Ω，使電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)(qi)(qi)選擇(ze)(ze)范圍寬。當采(cai)用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻或(huo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)子負載(zai)時，可(ke)能(neng)會(hui)發生某種不穩(wen)定(ding)性。增(zeng)加(jia)300Ω電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi)(qi)與PROG引(yin)腳電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)(qi)(qi)串聯(lian)(lian)或(huo)在輸(shu)(shu)出置10μF電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)(qi)(qi)能(neng)改善(shan)穩(wen)定(ding)性。在輸(shu)(shu)出不需要用(yong)陶瓷電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)(qi)(qi)，因(yin)為(wei)(wei)(wei)在很(hen)輕負載(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流聲頻下開(kai)關變換(huan)器(qi)(qi)(qi)(qi)(qi)變得(de)不連接和在下降周期(qi)開(kai)始時電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)(qi)(qi)會(hui)造成噪聲，應該采(cai)用(yong)鉭電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)。輸(shu)(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)選擇(ze)(ze)由充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)(qi)(qi)輸(shu)(shu)入(ru)紋(wen)波電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流（一般(ban)為(wei)(wei)(wei)最大輸(shu)(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流的1/2）決定(ding)。對于4A充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)(qi)(qi)建(jian)議用(yong)22μF（50V）陶瓷電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)(qi)(qi)，它一般(ban)可(ke)處理(li)2A紋(wen)波電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流。

　　從電池到(dao)墻(qiang)(qiang)式(shi)適(shi)配(pei)器的電流(liu)保護由P-溝(gou)MOSFET（Q1）提供。電壓(ya)比較器監控跨接在(zai)MOSFET上(shang)的電壓(ya)而且當墻(qiang)(qiang)式(shi)適(shi)配(pei)降到(dao)電池電壓(ya)之(zhi)上(shang)小于200mV時(shi)關閉MOSFET。盡管價廉的二(er)(er)極管可(ke)用于替(ti)代以MOSFET，但MOSFET只增加(jia)100mV到(dao)0.4V低壓(ya)差工作模式(shi)而不產(chan)生額外的熱(re)量。在(zai)沒有電池起(qi)動時(shi)間(jian)，采(cai)用MOSFET附加(jia)二(er)(er)極管使墻(qiang)(qiang)式(shi)適(shi)配(pei)器電源能達到(dao)Vcc引腳并(bing)為PWM控制電路(lu)供電。

　　主要的補償是d PROG引(yin)腳(jiao)上(shang)進行；然而DAC脈沖濾(lv)波(bo)要求確定電(dian)(dian)容(rong)器(qi)(qi)有(you)效值(zhi)。脈沖紋(wen)波(bo)電(dian)(dian)流必須(xu)小(xiao)平200mV或環路(lu)起(qi)伏（在(zai)輕載充電(dian)(dian)電(dian)(dian)流時出現(xian)的環路(lu)不穩定性）。Vc引(yin)腳(jiao)電(dian)(dian)容(rong)器(qi)(qi)的主要功能是提供自啟(qi)動支(zhi)持。必須(xu)有(you)一個1.5K電(dian)(dian)阻器(qi)(qi)與(yu)Vc引(yin)腳(jiao)電(dian)(dian)容(rong)器(qi)(qi)串聯以能恰當(dang)停(ting)機。

　　從熱觀點考(kao)慮，輸出電(dian)壓在電(dian)池溫度充(chong)電(dian)范圍內保持大約0.5%精度。精度越(yue)高(gao)，電(dian)流充(chong)電(dian)容(rong)量就越(yue)大，而更重要是在電(dian)池中與電(dian)壓基充(chong)電(dian)終端電(dian)路有關的問題就會更少(shao)。

　　關于SMBus加速泵，AC適配電流(liu)限制，安全信號感(gan)測，安全電壓和電流(liu)范圍設計等問題在此就不(bu)一一詳述。

　　LTC1579遵從智能電池系統組織發表的智能電池充電器標準。充電器控制器也遵從Intel的ACP標準，甚至當沒有AC墻式適配器電源時也能響應系統指令。該充電器提供最寬的電流和電壓工作范圍。LTC1759具有價廉、高性能和安全的特點，比其他智能電池充電器優越。